Cowan…to make a little more sense out of the pressure needed for the 2nd octave, keep this in mind: To begin, and for the most part, keep the chanter resting on the knee, sealing off any air leaks. Cover all finger holes and apply light to medium pressure on the bag.
At this point no sound, and no air, should escape from the chanter (or from the bag or bellows). Air is wanting out. Pressure is felt at the finger holes. Lift one finger, or two, per note, depending on the note desired, and you should get the lower octave.
I’ve seen beginners play all the notes in the lower octave, with the chanter off the knee, and it sounds kinda okay (out of tune), but that’s not really the way to do it. And, they could never get the upper actave that way, with a normal reed.
All air pressure comes out of one finger hole only to get into the 2nd octave. This triggers the reed into a double vibration. After the 2nd is achieved, you can often get other notes within that octave (A and above), with more than one finger lifted, and the reed will stay in the double vibration, depending on pressure.
The trick of the lifetime is the ability to keep or change the reed in, or into, a single or double vibration mode.
While playing the lower octave (with steady pressure), if you only lift one finger (the index) the upper G will automatically sound. If you lift two fingers (index and middle) only the lower octave will sound. If the upper G doesn’t automatically sound, your reed is usually too stiff, or opened up to much at the lips, depending on the climate. If it goes into the upper octave too easy, the lips are too thin or the reed is not opened up enough.
Lifting the chanter slightly, at the same time you lift the middle finger of the lower hand (upper F#), will produce the “barking” effect, and will encourage the reed into a double vibration.
For a while, the upper E, F# and G are the only notes that will get you into the upper octave. A (and above) is usually difficult to get into until you are already up in the area. That will come later with “popping.” But, some reeds have trouble with a clear upper E.
Never get the reed wet, nor stick it in your mouth. I’ve actually seen people do this who didn’t understand dry reeds too well.